1. Field of the Invention
The invention relates to a measuring device with a roll gap transmitter for direct detection of the height or the size of a roll gap between two working rolls in a roll stand. The invention additionally relates to the associated roll stand and a corresponding method.
2. Description of the Prior Art
A measuring device for detecting the gap of a working roll pair as an actual value for a regulator for keeping the height of the roll gap between the working rolls constant is known from German Patent Specification DE 24 04 763 C2. The measuring device comprises a measuring head which is aligned in the roll gap with the help of a scissor lever pair biased with the assistance of tension springs. The measuring head is held at the roll stand by way of a pivotable linkage. The measuring head comprises two electromagnetic measuring systems, which each detect the spacing of the individual reference plane from the associated shaft projection acting as a magnet. Through the pivotable linkage, which is dimensioned to be substantially longer by comparison with the height of the measuring head, it is ensured that uniform vertical movements of the working rolls such as, for example, vibrations are virtually without influence on the measurement result, because the spacing of each reference plane of the electromagnetic measuring systems from the associated shaft projection can be kept constant by the measuring device.
It is disadvantageous with this prior art that the pivotable linkage is merely designed to cause the measuring device or the measuring head to track a vertical movement of the working rolls in order to keep the spacing between measuring head and shaft projection of the working rolls constant. Problems with a horizontal movement of the working rolls in or against the rolling direction are not discussed.
U.S. Pat. No. 2,032,584 discloses a roll gap transmitter for detecting the height of the roll gap between two working rolls for a manual operation. It is not coupled with the roll stand and therefore cannot be used in any desired position of the working roll pair.
Finally British Patent Application GB 886 238 discloses a measuring device for measuring the size of the roll gap between two working rolls. The measuring device comprises two measuring rolls which are mounted by a common mount and are brought into contact with the surface of the working rolls for measurement of the size of the roll gap. The measuring rolls are biased by way of a linkage and a compression spring in the direction of the rolling gap plane which is spanned by the two longitudinal axes of the working rolls. The biasing represents a working point of the compression spring. Any change in the size of the roll gap, i.e. any vertical movement of the working rolls relative to one another, leads to a change in the spring force with respect to the working point. This change in the spring force, which represents a change in the size of the roll gap, is displayed on a display device.
The measuring device according to the British patent application serves, as stated, for detecting vertical movements of the working rolls relative to one another, i.e. a change in size of the roll gap with unchanged horizontal position of the working rolls. A displacement of the working rolls in or against the rolling direction would have the consequence of displacement of the working point of the spring and thus an increasing level of measurement inaccuracy. Starting from this prior art the invention has the object of developing a known measuring device as well as a known roll stand with the measuring device in such a way that the measuring device still supplies satisfactorily usable measurement results, without losses in measurement accuracy, even in the case of displacement of the working rolls in or against the rolling direction.